Long-Term Soil Drought Limits Starch Accumulation by Altering Sucrose Transport and Starch Synthesis in Sweet Potato Tuberous Root

Minfei Sheng, Houqiang Xia, Huizi Ding, Dongyu Pan, Jinping He, Zongyun Li, Jingran Liu

Int J Mol Sci.; 2023 Feb 3; 24(3):3053. doi: 10.3390/ijms24033053.

Abstract

In this study, the influences of long-term soil drought with three levels [soil-relative water content (SRWC) (75 ± 5)%, as the control; SRWC (55 ± 5)%, mild drought; SRWC (45 ± 5)%, severe drought] were investigated on sucrose-starch metabolism in sweet potato tuberous roots (TRs) by pot experiment. Compared to the control, drought stress increased soluble sugar and sucrose content by 4-60% and 9-75%, respectively, but reduced starch accumulation by 30-66% through decreasing the starch accumulate rate in TRs. In the drought-treated TRs, the inhibition of sucrose decomposition was attributed to the reduced activities of acid invertase (AI) and alkaline invertase (AKI) and the IbA-INV3 expression, rather than sucrose synthase (SuSy), consequently leading to the increased sucrose content in TRs. In addition, starch synthesis was inhibited mainly by reducing ADP-glucose pyrophosphorylase (AGPase), granular starch synthase (GBSS) and starch branching enzyme (SBE) activities in TRs under drought stress, and AGPase was the rate-limiting enzyme. Furthermore, soil drought remarkably up-regulated the IbSWEET11, IbSWEET605, and IbSUT4 expressions in Jishu 26 TRs, while it down-regulated or had no significant differences in Xushu 32 and Ningzishu 1 TRs. These results suggested that the sucrose-loading capability in Jishu 26 TRs were stronger than that in Xushu 32 and Ningzishu 1 TRs. Moreover, IbA-INV3, IbAGPS1, IbAGPS2, IbGBSSI and IbSBEII play important roles in different drought-tolerant cultivars under drought stress.

See https://pubmed.ncbi.nlm.nih.gov/36769375/

Figure 1

Sugar contents in sweet potato TRs under long-term soil drought stress in 2018 and 2019. * means significant at p < 0.05 among the three SRWC levels; ** means significant at p < 0.01 among the three SRWC levels.